Method of oxidizing ammonia



March 22, 1.932 T. FxscHER ET AL METHOD oF OXIDIZING AMMoNm` Filed June24. 1927 2 Sheets-Sheet Fig. 1.

We. mm/ MM/ r HZ fw@ f ma 7@ March 22, 1932 T. FlscHr-:R ETAL Filed June24. 1927 METHOD OF OXIDIZING AMMONIA 2 Sheets-Sheet 2 UNITED sT'Afrirs4Patented f Maa-22, y1932 f PATENT foFFIjcE .i`

THOMAS' rrscHERAND RUDOLF` WENDLANDT, 0B BIEsTBRRITz GERMANY,issvIofNoRsu To NIcoDBMcARo, B BERLIN, GERMANY, AND` ALBERT R.l FRANK,`oil? BERLIN-2 ordinary pressure. se

HALENSEE, GrERdVLANY :METHOD .oR oXI-DIzING AMMONIA` f kAmumtnm fue@JuneY 24, 1927,.,seri1 No. 201,266, and in Germany-*June [29, 1926.*

With the'known methods for the manufac-y ture of nitrogenfoxygencompounds ork of nitric acid'f'rom gasy mixtures containing am-v moniaand oxygen it'has up tonow notbeen possible in practice t'ofobtain a`complete ,conf Version of the nitrogenjsupplied injthe'form of ammoniainto nitrogeneoxygen compounds.` Accordingtothe proposals hither-` Ytoxinade the mixture`v of ammoniaandV air is either preheatedby theheatof thel discharg-` ing gases before conveying it to the Contact, or themixture is caused to takeup heat from the contact by wayjof radiation.There exists, however, the danger that the ammonia will be decomposed byundue superheating Now it has been discovered that an increase of theyield nmay be ,obtained by cooling the mixture of ammonia and air priortoy being permitted to gettingaccess to the catalyzer. As to thevariation of the concentration of the ammonia orthatjofthe oxygen inthegas mixture it mustg'beunderstood thatall proposals hitherto' made havefailed `"for the reason `that with' ammoniafoxygen con` centrationincreasingabove 1'0 v01. of ammonia the contact temperature will beraised to an impermissible value, and" reach as early as at 16 vol. thelo'vverlimit of explosion at The following method has provedparticularlysuccessful in order to obtaingan ener-` getic cooling. Aylayer ofliquid is provided yinthe pathl of motionof the gas which willthusbe caused tofcontinuousl'y passth-rough this layer of 'liquid in theform of numerous fine bubbles.`` Therefmay beprovided a layer of liquidextending over the whole width off the contact. Inthis manner no heatwill pass back to the contact, 'neither by'radiationnor by lreflection,the liquid. onl'the contraryabstracting a large part of the convectionheatl; and of the radiatedheat jiromV the contact.VK

The' layer of liquid maybe yprovided iny the rear of or above theIcontact-zone, preferably,

however, said layer of liquid'is provided in front or below the contact.t In,l the latter case i the' fresh gas 'will' Ithus be' causedtocontinuouslyV pass through said layer ofy liquid in yth'eform ofnumerous ne bubbles. Owing to-'the fact, that `rthe gas bubbles passinces-f santly'through said layer, the upperv surfaceof the latter willbe permanently interrupted," and no heat will pass `back tothe contactby radiation`V nor by reiiectiomthe `said surface of the liquid, on thecontrary, takinggup a' large part 'of heat. The amount of heat ab'-sorbed willnow be` able to produce a proper amount of water-steam, whichwill mixjwith the 'fresh or live-gas and increase the heat capacity ofthe same during-'passing the conf tact.

In this way .the contact temperature lmay i be reduced and regulated to'such any extent that it willbe'possible to maintain with mixtureskcontainngfa high percentage of ammonia thattemperature whichis mostfavor-y able for the conversion. The improved meth od may be carriedthrough with the aidfof the device.illustrateddiagrammatically and by Ywards in the direction indicated by the ar- 1 rows a2 in Figsl and 2through a hollow con-.

Vtainerl suited tocausesaid mixture toy undergo combustion'attheplatinum contact. A

`few cin-'belowthe doublefcontact net 2which,A

for example, may 'consist of platinum or alloys. f-

of platinum is arranged a sieve or perforated sheet metal Bwhich servesfor supporting "a layerl 4 ofliquid which may be supplied through a pipeAand conducted through an,

Yis retained upon the sieve merely by action of capillarity. Y Instead of the sieve 3 a wiref t net with 'lineshes of the properv size *may/be'used, so thatthe combustion mixture willpass oppositely located pipe B.The perforations ff; y

through the layer of water-4. If specialprd.

visions shall be'rmade to prevent the-water,

' needed. y

when passing out of said liquid, from forming b-ubbles or to scum or tobe squirted or the like, a further wire-net 5 having comparatively largemeshes may be arranged immediately above the surface ofthe layer ofliquid 4, which wire-net, however, does not act as contact.` Instead ofsaid wire-net `5 also a perforated sheet-metal piece may be used whichis preferably so designed that'it cuts thebubbles. v

About 1 cm. above the layer of water there is located the contact layerwhich, for instance, may consist of a platinum wire-net 2.

The distance between said platinum wire-net and the liquid layer,however, may'also be essentially larger, for instance 20 cin. In generalWe wish to be understood that the sizes of the meshes as above given areintended to serve as an example, and that the sizeof said meshes aswellas of other elements of the apparatus may be changedin accordancewith other circumstances.

Y The radiationheat which the layerof liquid hasabstracted from thecontact will cause vaporization of the water over the entire sectionalarea with the effect, that the Water is supplied continually in suchy an.amount that its thickness upon thesieve remains practically constantor, in other Words, that the amount of water which evaporates does notexceed the amount required for the regulation of the temperature. V Witha device as above described it isrendered possible to oxidize, forinstance, a dry mixture containing as much as l2O vol. of ammonia andevenmore with a conversion of about'95 to 96% with a supplyT of steamfrom the layer of only 10 vol. V%. p ammonia supplied will be obtainedas an acid of a specific gravity of 1.4 and more, if the process, forinstance, is carried out by Lindeair containing of oxygen. In this casethe average output of the working element will be 25% larger andthecondensation space only from 1/10 to 1/50 ofthat otherwise Owing to thereduction of the reaction temperature and the increase of theheatcapacity of thereaction mixture anyV danger of explosion. will becompletely obviated. In the case of extraordinary troubles which mayarise `in connection with the operation of the apparatus, such as forinstance in case of uncontrollable strong variations of the compositionof the mixture, as well as of variations of the pressure, the layer ofwaterf will presurface of the layer of water and the Contactnet,therefore, no directed explosion wave,

and in particular, no detonationcan arise'. Also, the wave ofthedetonation, if arising at all, would notbe able to pass the closurepresented by the layer of water.

. In particular cases thesteam pressure of In this manner 94 to 95% ofthe the water zone and the amount of the steam generated out of thewater may be controlled y cooling or by heating.

In the modification shown in Fig. 2 a cooling or heating pipe or also aheating coil 6 is arranged within the layer of liquid. Thesteam-pressure of the water zone and the amount of the steam may also bea'tlected by substances which are dissolved or distributed in the Water,or if steam is added, the quantity of added steam may be changed.Instead of employing a layer of water as cooling agent, the cooling Zonemay also be supplied with ammonia-water, and the ammonia-gas dissolvedin the water may be evaporated and a more diluted ammonia mixture or anoxygen-nitrogen mixture which is free of ammonia may be caused to passthrough. the ammonia Water.l The layer of Water may also be utilized forpurifying the fresh or live-gas, for instance, with the aid of suitableadmixtures. Also ammonia salts maybe dissolved in the liquid and NH3 maybe liberated either by steam or by the action of alkaline substances.There may also be used several layers of liquid,.one in the rear of theother.

According to Fig. 3 the combustion air is carried through the conduit 7into the regulating valve 8 towards the` under vaperture of the element9 of the combustion apparatus'. The element 9 of the combustion appa-'ratus comprises a. mixing device, the ammo- 13 is slightly arched asindicated in Fig. 3.0i

the drawings in order to expedite the circulation of the liquid andbringabout a thorough f mixing of the latter upon the sieve 13. The

further sieve 14 which is arranged above the sieve 13'will form theupper limiting wall for the emulsion of gas and liquid positionedintermediate Vthe two sieves'13 and 14. The compositionA as well yas thetemperature of the gas-mixturewill be regulated by the comf YVposition'and the temperatures of said layer senta complete protectionagainst explosion.- In the very narrow Zone between 'theupper of liquid.The so regulated gas-mixture passeslthrough the sieve 14 tothe Contact15 consisting, for instance, of one or more nets ther auxiliary devices18, 19, 20, 21, 22 and 2.3 serve for conveying the liquid to the sievefmay be treated according to our invention.

13, and for: the;V automaticf 'regulation of `the layer ofgas@and,liquid`positioned intermediate saidfsieves 13e-`and 14.'.1fTheliquidv to beconveyed to the sieve 13 iows .through the.

pipe 18 and thereuponfthrough the pipe, 19 towards the center of thesieve.` Special care VVmay further be taken in order to evenlydistribute Asaid liquid over the sieve 13. Anex-Y V cess of liquid lonthe sieve lfmay iiow .oif

through the pipe `or conduit 21 and the siphon 20`towards the outside'.The siphonk20 may be rotated aroundthe pipe 21 and according as'towhether said Siphon 20 will be more or less inclined towardsjthehorizontal plane the level of the layer of gas and liquid 4may.

be adjusted in vertical direction or its averagel density may -fvberegulated. The aperture 23 and the yflexible pipe 'or' conduit'22cludesthose vprocesses in which the walls ofk the reaction space aresimultaneously cooled or in whicli'devices for preventin'gradiationV orfor cooling are provided at the nitric oxide side of the contact. n I

A- particularrv ladvantage of our present process as vregards thecoolingof the contact in connection with a layerof liquidisthepossibility ofk admixing steam which exerts an extraordinarily effectivecooling actionry this being `due to the large heat capacity of steam. Ithas furtherv been found "that the admixture of the elementary hydrogento the, f

initial mixture will act favorably upon the 1 reactionA process, thatisgto say, the yield ob-.y Y tainable in this Way may be raised as comepared withthe yield attained -without an ad- -f mixture-of thelkindstated.'V

i serveto render Vthe auxiliary devices inde pendent from the pressurewhich :prevailsV in the interior ofthe vapparatus shown in Fig. 3.By-meansiof the pipe 25 with thel v valve 24 therein steam may beintroduced into the layer intermediate ythefysieves 13 and 14 forregulatingnthetension'iof said liquid according to demand. The steam,however, may also be introduced in front of thelayer of liquid, forinstance, in front of the sieve 12.Y

Thev process accordiner to our vinventionV is not limited to theapplication of a layer of a liquidl formed merely by water; VThe layerof liquid provided above the sieve may also consist ofanotherpliquidproducing,a vapor which does not affect the process ofcombusn tion of the ammonia. Also a liquid may be used having aninherently low pressure with relation to the service condltlons, or theprest sure of the liquid may berendered very small by properly coolingthe same.

From the above description it will be ap more can be used. The oxygenconcentrationy of the gas mixture varies correspondingly, and byaddition of Lindeair (oxygen contents -70%) strongly enriched withoxygen or by the addition of pure oxygen lit will also be possible tokeep the mixture upon a suiiiciently highconcentration, it being pref-`erablev in this case to maintain the stoichiometric proportionbetweenammonia and oxygen. For instance, also a non-diluted mix ture of Ivolume part of ammonia with from one to three volumeparts of pureoxygen, for instance 1.7 volume parts of pure oxygen,

It may further :be remarked that our present process may advantageouslyalso 'be combined withany of the known processes or devices `which servefor cooling the apparatus.V Our invention consequently also inf.consequence thereof, the combustion of lam-.1 -monla under a pressurehigher than 1 atm. will render possible tocondense nitric oxides tricoxides by meansV of our new process'and,

nitrogen,` or for carrying `through thek am-l It willbe evidentlatoncethat our present Y process andthe various'.modicationsof thevsame will produce a particularlyfavorable eect inf all those 'casesiniwhichthe reaction gas is conducted to the contact at some higherpressure. Y In ycase Y of combustlon lunder presof space will rise inaccordance .with theconversion, the same as the radiation heat; Itv

will therefore be obvious f that' by "means, of the device hereindescribedthe most^favorable contact temperature `may be .maintainedKAVwith the greatest degree of'certainty.- f Iny Y under increasedpressure into nitric acid im-v mediatelyv subsequent to the processwhich is carried out by the combustion el-ement.

' The possiblity ofcondensationof the ni-v its modifications `will yielda high% acid, as

well as a high% nitrogen in thewaste ases n said nitrogen containingonlyextraor inary slight amounts of nitrose gas that can bev easilyL'removed by employing a preliminary process of purification.'VV Ourinventionalso.

includes a modification" of 'the process by which said nitrogen isutiliz-ed either for azotizing the carbide of theearth-alkalies,

that: is toV say, for the'V manufacture kof ilinie monia-synthesisafteranfappropriate admix-` ture fofhydrogen."

Weclaim: Y y

o rfoxygen-containing;,gas, said process consisting in inserting alayer.of liquid `in the path ofthe gas in proximity to the vzone offV .thecatalytic contact and passing themixture of gas through said layer ofliquid in the form` of bubbles, said liquid being: adapt'eolpito ab`sorb'heatr fromv thefcontact.` v i f2. The herein-described,process ofmaking 1. The hereindescribed process of makingl 'a 'highgrade nitric`acid l:.or other nitrogenfv oxygen compounds .by catalytic oxidation ofammonia or the like in mixture with oxygen sure 'the amount of heatgeneratedper unitr a high-grade nitric acid or other nitrogen oxygencompounds by catalytic oxidation of ammonia or the like in mixture `Withoxygen tion of the gas in front ofthe contact zone ofk a catalyzer alayer of liquid, and causing the mixture of'gas to pass through saidlayer of liquid to the contact of the catalyzer in the form 4of bubblesand causing said liquid to labsorb heat from said Contact by Wayi ofradiation and tol evaporate partly into said mixture, the level of saidlayer of liquid being positioned in close proximity to said contact toprevent a directed explosion as Well as aV Wave of explosion arising inthe narrow space intermediate said liquid.

4. TheV herein-described process ofmaking contact and said layer ofVwhich the gas which has not undergone reacwhich the mixture ofV gas iskeptunder a pressure higher than atmospheric pressure.

12. A process as specified. by claim 4, in which the mixture of gas iskept underk a pres sure higher than atmospheric pressure.

13. A process as specifiedl by claim 5, in Which the temperature of theliquid and the tension of the vapor produced' therefrom are regulated byintroducing steam at a place in front of the contact Zone into saidliquid.

14. A .process as specified by claim 5, in which the temperature of theliquid and the tension of the vapor produced therefrom are regulated by'introducing steam into said liquid. v Y

In testimony whereof We afiix our signa.

tures.

THOMASy FISCHER. RUDOLF WENDLANDT.

a high-grade nitric acid or'other nitrogen-V oxygen compounds bycatalytic oxidation of ammonia or the like inmixture With an oxygen oroxygencontain1ng gas, said process consisting in providing Within thepath of motion of the gas a layer of liquid in proximity to the Zone ofthe catalytic contact to absorb heat therefrom, and passing the gasmixture through said layer of liquid in the form of bubbles, said liquidcontaining a substance, suchl as a solution of ammonia,

affecting pressure ofthe vaporgenerated from said liquid.

5. The herein-described processA of making a high-grade nitric acid oroxygen-nitrogen compounds by catalytic oxidation of ammonia or the like,said process consisting in providing a layer of liquid within the pathof motion of the gas through the catalyzer, Y passing the gas throughsaid' layer in the form of bubbles, causing said liquid to absorb heatfrom the contact ofthe catalyzer by radiation y and to partly'evaporateinto .the mixture of kmentary hydrogen.V

fresh gas, and regulating the temperature of said liquid and the tensionof the vapor produced therefrom. 'f n 6. A process as specified by claim"1 in Which to the initial mixture there is `added ele- 7. A process asspecified by claim 2 in which tothe initial mixture there is added byclaim 1,7in'

